The iPhone app the phone carriers hate

It's an interesting app, called CarrierCompare, and it's free.  It looks at how good, and fast, your iphone phone service is at the location you're currently at, and then compares it to the results others have reported in the area.  At my parents' place in the Chicago burbs, it's claiming that AT&T is better.  That's not true, at least not in my experience.  I had to drop AT&T and switch to Verizon because I couldn't get more than one bar on my AT&T iPhone at mom's place, or in the neighboring towns (having said that, my parents who have AT&T, but not with an iPhone, have great coverage at home). Now at least with Verizon I have service, though my service in DC with Verizon is now worse than my service was with AT&T.  Sigh.  We're so not #1 sometimes.

I'm curious what you guys have found, in terms of which service you prefer on your iPhones (or other phones), but also whether non-Americans have the same spotty service in their countries.  I know Chris has had problems with his iPhone service in Paris, but now with his previous phones.  More from CNN.